The spore-forming microorganism Bacillus thuringiensis (B.t.) produces the best-known insect toxin. The toxin is a protein, designated as .delta.-endotoxin. It is synthesized by the B.t. sporulating cell. The toxin, upon being ingested in its crystalline form by susceptible insect larvae, is transformed into biologically active moieties by the insect gut juice proteases. The primary target is insect cells of the gut epithelium, which are rapidly destroyed. Experience has shown that the activity of the B.t. toxin is so high that only nanogram amounts are required to kill susceptible insect larvae.
The reported activity spectrum of B.t. covers insect species within the order Lepidoptera, which is a major insect problem in agriculture and forestry. The activity spectrum also includes the insect order Diptera, wherein reside some species of mosquitoes and blackflies. See Couch, T. L., (1980) "Mosquito Pathogenicity of Bacillus thuringiensis var. israelensis," Developments in Industrial Microbiology 22:61-67; Beegle, C. C., (1978) "Use of Entomogenous Bacteria in Agroecosystems," Developments in Industrial Microbiology, 20:97-104.
Krieg et al., Z. ang. Ent. (1983) 96:500-508, describe a B.t. isolate named Bacillus thuringiensis var. tenebrionis, which is reportedly active against two beetles of the order Coleoptera. These are Colorado potato beetle, Leptinotarsa decemlineata, and Agelastica alni. This is the only known B.t. isolate reported to contain such activity; all previously identified B.t. strains have had activity against caterpillars (order Lepidoptera) or larvae of certain flies (order Diptera).
The Krieg et al. B.t. isolate is not available for side-by-side comparison with the B.t. isolate used as the source of the novel B.t. gene of the subject invention. Therefore, since the Krieg et al. B.t. isolate is not available to the public, the Krieg et al. publication is not a valid patent law reference under U.S. law.